In order for micro-electro-mechanical system (MEMS) switches to be practical for use in microwave circuits, MEMS switches must be enclosed in a hermetic package which can exclude moisture for many years. Since the cavity around the MEMS switch must be very small, an extremely low leak rate is required. The package must also be compatible with a low-loss microwave circuit which includes transitions, vias, in and out with a minimum of parasitics and loss.
Moreover, MEMS switches to be practical for use in microwave circuits, the cost of manufacture needs to be relatively low. More specifically, to realize this low cost, a wafer scale process for simultaneous packaging of thousands of circuits having the smallest possible chips sizes would have to be utilized.
Therefore, it is desirable to provide a low cost, low loss hermetically-sealed package for MEMS switches. Moreover, it is desirable to provide a packaging design and process which can provide a hermetic environment for microwave circuits and devices, such as MEMS switches, by combining some of the outstanding properties of single crystal silicon, silicon on insulator, tungsten vias, cavity and post etching in silicon, unique circuit design, and thermo-compression gold bonding. Also, it is desirable to provide a packaging that enables integrated broadband (DC-110 GHz), low-loss, high-isolation, very low-dispersion interconnects, and easy integration into complex circuits by the use of flip-chip bump bonding techniques. Furthermore, it is desirable to provide a packaging that is applicable to mechanical and electromagnetic packaging of a variety solid-state, MEMS, passive microwave structures, and MEMS switches.